PURPOSE:  To improve the air quality in metal/nonmetal mines to reduce the risk of adverse health effects from worker exposure to airborne contaminants such as diesel particulate matter (DPM), toxic fumes from blasting, and silica dust.

RESEARCH SUMMARY:  Virtually all underground stone mines and many other metal/nonmetal mines have large openings creating ventilation airflows with low velocities. Due to the ventilation inefficiencies common to these mines, the underground workers are exposed to a variety of potentially harmful substances through the air they breathe. Reductions in worker exposure to these contaminants can be achieved by improving the ventilation airflow in these mines. These goals are particularly timely in that the metal/nonmetal mining industry is confronted with new DPM regulatory exposure limits that were set forth in 2002, with more stringent restrictions scheduled to take place in 2006.

Practical methods to improve ventilation airflows in large opening mines are being investigated. Several methods have been conceived, developed, and evaluated in operating large opening stone mines that have been shown to improve the general air quality in the underground workplace. These methods include: (1) identifying the proper fans for use in large opening mines; (2) including ventilation needs as an integral part of the mine planning process to aid the development and use of efficient generic ventilation designs for all mines; (3) developing a computer program to determine the approximate air flow volume necessary to meet statutory air quality (DPM) requirements based on the diesel equipment in use at an individual mine site; and (4) improving the construction methods and materials used to construct stoppings for directing mine ventilation air to the critical areas of large opening mines to reduce worker exposure to airborne contaminants.

Although there have been many general improvements in large opening mine ventilation practices resulting from the current research effort, the current state of the technology for addressing very site specific contamination areas in large opening mines is still the random and unscientific placement of auxiliary ventilation fans in the working areas. Additional research will develop optimum methods for getting higher volumes of non-contaminated mine ventilation air to the working areas, i.e., increasing the ventilation efficiency. This will be accomplished by developing novel mining methods to direct the ventilation airflow to the working areas, including the use of using long stone pillars and auxiliary fans. At the conclusion of the research effort, Best Practices for improving ventilation airflow in large opening mines will be made available to the metal/nonmetal mining industry to reduce workers exposure to airborne contaminates in large opening mines.